The invention relates to a process for improving the filling capacity of tobacco material by expanding moist tobacco material by means of pressure reduction and subsequent drying to the processing moisture content.
Numerous processes for expanding tobacco material are known. In these processes, cut tobacco ribs or tobacco leaf material is subjected, while moist, to a more or less intense increase in temperature or reduction in pressure. The rapid evaporation of the liquid contained in the tobacco, for example water or organic solvents, leads to a greater or lesser expansion of the tobacco cell structure. The disadvantage of these processes is that the expansion ratio is to a certain extent unsatisfactory and that the expanded structure is at least partially lost again during subsequent processing.
The arrangement of a Venturi nozzle at the end of a drying stage for tobacco material is known from German Offenlegungsschrift No. 2,637,124 (see FIG. 4).
Tobacco expansion cannot occur here, as the Venturi nozzle is located at a point in the apparatus where the tobacco has already been dried. Tobacco dried in this manner no longer has the elasticity necessary for expansion. In contrast to this, in the process of the invention, the tobacco passes through the expansion stage in the moist state and is dried only subsequently.
The present invention is directed to a process of the type mentioned in the introduction, but in which tobacco material in the moist state is subjected, within an extremely short period of time, to pressure reduction and at the same time to a sharp increase in temperature. The resulting abrupt evaporation of the liquid contained in the tobacco material leads to an improvement in the filling capacity of the tobacco material of 30 to 100%, without the tobacco cell structure being destroyed to any notable extent. In spite of the high expansion result, the structure is preserved even during further processing of the tobacco material.